1. Define amphibian communities appropriate for evaluating restoration success. 2. Develop methods for measuring the area occupancy of amphibian communities across habitats and environmental gradients. 3. Investigate the relationship of occupancy, survival, movement probability, and density with hydroperiod and other environmental factors. 4. Develop restoration targets for the amphibian community of the Everglades. 5. Develop a restoration tool for amphibian communities that measures restoration success and compares restoration alternatives. 6.Develop an index of biological integrity for amphibians that provides a framework for scientifically defensible decisions by restoration managers.
Kenneth G. Rice Frank J. Mazzotti; H. Franklin Percival, Unpublished Material, Use of Amphibian Communities as Indicators of Restoration Success.Online Links:
U.S. Department of Agriculture - Natural Resources Conservation Service (NRCS) Department of the Interior - U.S. Geological Survey Department of Commerce - National Oceanic and Atmospheric Administration (NOAA) Environmental Protection Agency (EPA) Smithsonian Institution - National Museum of Natural History (NMNH)
Project personnel include Hardin Waddle, Amanda Rice, and Brian Jeffrey.
954 577-6305 (voice)
954 577-6347 (FAX)
ken_g_rice@usgs.gov
Amphibians are present in all habitats and under all hydrologic regimes in the Everglades. The species present and the occupancy rate of a given species differ greatly across those gradients. These differences are due to hydropattern, vegetation, and other environmental factors. The combination of species composition and proportion of each habitat occupied at a given time form unique communities defined by those environmental factors. Therefore, if these communities can be reliably defined and measured, Everglades restoration success can be evaluated. This project will develop methodologies for defining and measuring the membership and area occupancy and of amphibian communities. Further, we will investigate the relationship of occupancy, survival, movement probability, and density of amphibians with hydroperiod and other environmental factors. Finally, we will provide a method for measuring restoration success based on these communities.The importance of amphibian communities to Everglades restoration has been recognized and listed as critical priority research needs.
The species will be identified in the field. Standard mark-recapture methods will be used to estimate survival, capture, and movement probabilities for amphibians in the Big Cypress National Preserve. Sampling sites will be chosen randomly and the sites will be sampled continuously in that order over consecutive days till all sites have been sampled four times.
1. Developing methods for defining amphibian communities. 2. Investigating the relationship of occupancy, survival, movement probability, and density with hydropattern. 3. Developing methods for measuring the occupancy rate of communities across habitats and hydroperiod gradients.
We will use 3 primary methods to accomplish the objectives of the project:
1. Proportion area occupied (PAO) by a species.-- One problem with many of the methods used to sample amphibians is the lack of any control of the myriad environmental factors that affect the behavior and activity of the animals. Many monitoring programs simply count animals and do not control for this observability or capture probability (p). Therefore, comparisons over time or space are not possible or are biased. Rather than mark the individual, we 'mark' the species. Therefore, presence/absence data from several plots within a habitat (or along a hydroperiod gradient in our study) provides an estimate of p and allows estimation of the proportion of a stratum occupied by a given species at a given time.
Sampling units will be chosen randomly with each stratum. Strata will be defined by the hydroperiod observed from existing hydrologic data and habitat type as defined by existing GIS vegetation layers. Our standardized sampling unit will be a circular plot of 20m radius. Plots will be sampled after dark to increase the probability of observing nocturnal amphibians. At each plot we will begin by listening for anuran vocalizations for 10 minutes. The abundance of each species will be categorized as: no frogs calling, one frog calling, 2-5 calling, 6-10 calling, >10 calling, or large chorus. The intensity of the vocalizations will be categorized as: no frogs calling, occasional, frequent, or continuous. After the vocalization survey, we will perform a 30-minute visual encounter survey (VES) in each plot. During this time, all individual amphibians observed will be identified to species and captured if possible. We will record the species, categorize the age (egg, larvae, juvenile, sub-adult, or adult), measure and record the snout-to-vent length and record the sex if it can be determined. We also will record the substrate and perch height of the animal. In addition to VES, in plots that are completely flooded, we will use dipnets and funnel traps to attempt to capture aquatic amphibians. We also will record several ancillary variables at each plot (air temperature, relative humidity, presence of water, water temperature, wind speed, cloud cover).
Individual species capture histories (matrix of presence/absence of each species at a sampling period and plot) and corresponding covariates (habitat, hydroperiod, temperature, humidity) will be assembled. We will then estimate the proportion of each stratum occupied by a species and the capture probability (using MLE and the logistic regression for covariates; MacKenzie 2002). The best model will minimize the amphibian community index (AIC) and adequately estimate the parameters in the model (the candidate model list will be developed a priori based on ecological knowledge and will not include all possible combinations). We can then use these estimates to construct appropriate communities for each stratum (see proportion of area occupied by a community below).
2. Mark-recapture.
We will use standard mark-recapture methods to estimate survival, capture, and movement probabilities for amphibians in Big Cypress National Preserve. We will use the Cormack-Jolly-Seber model to estimate the above parameters with maximum likelihood methods (Williams, et al. 2002). Further, we will use covariates such as hydroperiod to investigate the effects of hydrology on the population parameters. Our main objective is to define the controlling environmental factor on the population parameters. This factor will be used in the definition of communities (see proportion of area occupied by communities below).
Our study design will consist of drift fence arrays (we standardize distances between traps so that movement probability can be estimated) arranged across habitat and hydrologic gradients in Big Cypress National Preserve. Each fence will have approximately 6 traps (one on each end and one in the middle of each side). Each trap will have one or two funnel openings as appropriate and will be secured close to the ground and against the fence to prevent animals from going under the trap or between the trap and the fence. Each trap also will be covered with Masonite, burlap, or palm fronds to protect captured animals from exposure to direct sunlight and to help prevent desiccation. Each trap will be individually numbered across the entire array. A damp cloth or sponge will also be placed in each trap to allow captured animals to maintain moisture, but no bait will be used in the traps. We also will erect 3.5cm PVC pipes along each of the fences. These pipes are very effective at capturing treefrogs (Hyla, Osteopilus, etc.; Boughton et al. 2000), a group of animals largely missed by drift fences (Enge 1997).
Traps will be examined for captured animals and damage daily when open. Traps will be opened for one week per month. When not in use, traps will be removed from the area or will be collapsed and opened so that no animals will be captured between sampling periods. When animals are captured, they will be carefully removed from the trap to avoid harm. They will be identified to species, age, and sex whenever possible and measured snout-to-vent (SVL) and massed using a Pesola (TM) hanging scale. We will record the trap number of capture.
Captured animals will be individually marked. Marking method will depend on the taxon, but all methods will be those approved by the American Society of Ichthyologists and Herpetologists and the Society for the Study of Amphibians and Reptiles (<http://www.asih.org/files/hacc-final.pdf>). An animal care and use protocol (IACUC) has already been filed with the University of Florida detailing how pain and suffering of the captured animals will be minimized. Anurans (frogs and toads) will be marked using a commonly accepted toe-clipping scheme (Donnelly et al. 1994). Toes will be removed quickly with a pair of sharp scissors. We will remove no more than two toes per limb and we will not remove the first toe on any limb. Scissors and other equipment will be cleaned with alcohol to avoid disease transmission. Salamanders will be marked in one of two ways. Large aquatic salamanders (Amphiuma, Siren, etc.) will be marked with a passive integrated transponder (PIT) tag. The PIT will be implanted in the tail, which has been shown to be safe and permanent (unpublished data). Smaller salamanders with four limbs (Notophthalmus, Eurycea, etc.) will be marked with PIT tags if large enough, or they will be marked with toe clipping as described above.
All animals will be released as soon as possible after capture. Any animals that perish during the trapping or handling process will be collected and preserved as voucher specimens for the project. Trapping will take place from Monday through Friday on a trapping week. This will allow four trap-nights per week every week traps are opened.
3. Proportion area occupied by a community.
Given that species occupancy rates differ across hydroperiod gradients and that hydrology is the controlling factor of this difference, we can begin to construct 'communities.' This pattern of species composition and PAO forms the 'community' along the hydroperiod gradient.
At present, the method for defining and then predicting community composition and PAO is not complete. This study will develop this methodology for the Everglades. We will use data from preliminary studies (primarily recent and ongoing inventories of amphibians in ENP, BICY, and BISC) to choose the members of a given community and then model, within the PAO framework, those communities. As in PAO for a species outlined above, we will construct capture histories for each community and estimate PAO and capture probability. This community model can then be used to develop a amphibian community index.
Index of Biological Integrity. -- Indices of biological integrity (IBI) were originally developed to assess conditions of riverine systems (Karr 1991, 1993) and also have been developed successfully for use in terrestrial environments (O’Connell et al. 1998). The basic premise of IBI’s is that a range of conditions of ecological integrity can be defined based on the structure and composition of a selected biological community (e.g. amphibians, fish, birds, macroinvertebrates). The concept of biological integrity provides an ecologically-based framework in which species-assemblage data can be ranked in a manner that is more informative than traditional measures such as richness and diversity (Karr and Dudley 1981, Brooks et al. 1998). Therefore, the final step in this project will be to develop an amphibian community index (ACI) for evaluating the success of restoration and management of Greater Everglades Ecosystems. The ACI will be modeled after previously developed IBI’s (Cronquist and Brooks 1991, Karr 1991,1993, Books et al. 1998, O’Connell et al. 1998). Essentially, we will use the PAO of communities estimated above to index or define the integrity of a given stratum. As restoration proceeds, we can use changes in the index to make informed management decisions and to measure success. By providing a reliable and repeatable measure of ecological quality an ACI will help managers reach scientifically defensible decisions (Brooks et al. 1998).
Mark-recapture: At present, the method for defining and then predicting community composition and PAO is not complete. This study will develop this methodology for the Everglades. We will use data from preliminary studies (primarily recent and ongoing inventories of amphibians in ENP, BICY, and BISC) to choose the members of a given community and then model, within the PAO framework, those communities. As in PAO for a species outlined above, we will construct capture histories for each community and estimate PAO and capture probability. This community model can then be used to develop an amphibian community index. Index of Biological Integrity. -- Indices of biological integrity (IBI) were originally developed to assess conditions of riverine systems (Karr 1991, 1993) and also have been developed successfully for use in terrestrial environments (O’Connell et al. 1998). The basic premise of IBI’s is that a range of conditions of ecological integrity can be defined based on the structure and composition of a selected biological community (e.g. amphibians, fish, birds, macroinvertebrates). The concept of biological integrity provides an ecologically-based framework in which species-assemblage data can be ranked in a manner that is more informative than traditional measures such as richness and diversity (Karr and Dudley 1981, Brooks et al. 1998). Therefore, the final step in this project will be to develop an amphibian community index (ACI) for evaluating the success of restoration and management of Greater Everglades Ecosystems. The ACI will be modeled after previously developed IBI’s (Cronquist and Brooks 1991, Karr 1991,1993, Books et al. 1998, O’Connell et al. 1998). Essentially, we will use the PAO of communities estimated above to index or define the integrity of a given stratum. As restoration proceeds, we can use changes in the index to make informed management decisions and to measure success. Further, we can use the pattern of these communities based on hydopattern to develop restoration targets and to compare alternatives.
Developing methods for defining amphibian communities. Developing methods for measuring the occupancy rate of communities across habitats and hydroperiod gradients. Establishing restoration targets for amphibian communities in appropriate habitats. Developing models and methods to measure restoration success across these communities and compare restoration alternatives. Developing an overall index of amphibian community integrity.
Duellman and Schwartz (1958) produced the first scientific survey of the amphibians of south Florida. This work serves as an excellent reference for the historical distribution of many species before the extensive habitat loss in south Florida during the second half of the 20th century. Meshaka et al. (2000) produced a species list of the herpetofauna for ENP, but little information about the habitat associations and population status of the species was contained in that report. Dalrymple (1988) provided a good description of the herpetofauna of the Long Pine Key area in ENP, but no attempt has been made to sample amphibians throughout the Everglades.
We will use 2 primary methods to accomplish the objectives of the project: 1.Proportion area occupied (PAO) by a species. a. Vocalization survey b. Time-constrained searches 2. Proportion area occupied by a community.
Population Area Occupied by a species: Sampling units will be chosen randomly within each stratum. Within Everglades National Park these are along the Main Park Road and Context Road. We will choose 15 sites along each road accessed by foot. The sites will be located within 300 to 900 feet of the road. In Water Conservation Area 3A, we will select 15 sites in each stratum along a North-South transect from I-75 to SR41. Each stratum will be defined by the hydroperiod observed from existing hydrologic data and habitat type as defined by existing GIS vegetation layers. For hydropattern, a stratum will be defined for each 50 day difference (0-50, 51-100, 101-150, 151-201, 251-300, 301-365 days). Sites will be visited twice biweekly,April through September.
Our standardized sampling unit will be a circular plot of 20m radius. Plots will be sampled after dark to increase the probability of observing nocturnal amphibians. At each plot 2-3 person crews will begin by listening for anuran vocalizations for 10 minutes. The abundance of each species will be categorized as: no frogs calling, one frog calling, 2-5 calling, 6-10 calling, >10 calling, or large chorus. The intensity of the vocalizations will be categorized as: no frogs calling, occasional, frequent, or continuous. After the vocalization survey, we will perform a 30-minute visual encounter survey (VES) in each plot. During this time, all individual amphibians observed will be identified to species and captured if possible. We will record the species, categorize the age (egg, larvae, juvenile, sub-adult, or adult), measure and record the snout-to-vent length and record the sex if it can be determined. The animal will then be released at the original capture site. We also will record the substrate and perch height of the animal. A University of Florida Institutional Animal Care and Use Committee approval will be obtained for animal capture. In addition to VES, in plots that are completely flooded, we will use dipnets and funnel traps to attempt to capture aquatic amphibians. We also will record several ancillary variables at each plot (air temperature, relative humidity, presence of water, water temperature, windspeed, cloud cover). If any animals that are captured show signs of disease or are new exotic species, we will collect them for health assessment by the USGS National Wildlife Health Center and/or identification and preservation by the Park.
In addition, a maximum of 20-1m tall, 5 cm diameter PVC removable pipes will be installed in each site for refugia of treefrog species. During each visit, animals will be removed from the pipe for identification and measurement as outlined above. All animals will be released into the original PVC refugia. All PVC will be removed at the end ofthe study.
At 10 sites in ENP (5 along Context Road and 5 along Main Park Road) we will install a 20m drift fence for capture of aquatic salamanders. The drift fence will consist of 20m of removable erosion control fence with a funnel trap incorporated at each end and in the center. Traps will be placed along the fence for 5 consecutive days once per month during May through October. The traps will be checked each day in the morning to minimize heat stress on captured animals. Animals will be measured as outlined above and released at the capture site. All traps and drift fences will be removed during non-capture periods. All drift fences and traps will be removed at the end of the study. Both drift fences and PVC refugia will be placed behind vegetation to minimize views from the road if possible.
Individual species capture histories (matrix of presence/absence of each species at a sampling period and plot) and corresponding covariates (habitat, hydroperiod, temperature, humidity) will be assembled. We will then estimate the proportion of each stratum occupied by a species and the capture probability (using MLE and the logistic regression for covariates; MacKenzie etal. 2002). The best model will minimize AIC and adequately estimate the parameters in the model (the candidate model list will be developed a priori based on ecological knowledge and will not include all possible combinations). We can then use these estimates to construct appropriate communities for each stratum (see proportion of area occupied by a community below).
2. Proportion area occupied by a community: At present, the method for defining and then predicting community composition and PAO is not complete. This study will develop this methodology for the Everglades.
Index of Biological Integrity.-- Indices of biological integrity (IBI) were originally developed to assess conditions of riverine systems (Karr 1991, 1993) and also have been developed successfully for use in terrestrial environments (O'Connell et al. 1998). The basic premise of IBI's is that a range of conditions of ecological integrity can be defined based on the structure and composition of a selected biological community (e.g. amphibians,fish, birds, macroinvertebrates). The concept of biological integrity provides an ecologically-based framework in which species-assemblage data can be ranked in a manner that is more informative than traditional measures such as richness and diversity (Karrand Dudley 1981, Brooks et al. 1998). Therefore, the final step in this project will be to develop an amphibian community index (ACI) for evaluating the success of restoration and management of Greater Everglades Ecosystems. The ACI will be modeled after previously developed IBI's (Cronquist and Brooks 1991, Karr 1991,1993, Books et al. 1998, O'Connell et al.1998). Essentially, we will use the PAO of communities estimated above to index or define the integrity of a given stratum. As restoration proceeds, we can use changes in the index to make informed management decisions and to measure success. Further,we can use the pattern of these communities based on hydopattern to develop restoration targets and to compare alternatives.
Collection of additional field data on amphibian distributions in the Ten Thousand Islands and the Florida Panther National Wildlife Refuge to supplement existing data from the Big Cypress National Preserve
Collection of further information on cryptic species including aquatic amphibians within Big Cypress National Preserve
Aquisition of hydrologic data from different state and federal sources in southwest Florida and elsewhere in the Everglades to estimate hydrologic parameters of interest (mean annual hydroperiod, days since dry down, etc.) at our sampling locaton. This data will be used to finalize models of amphibians due to hydropattern in the Everglades
Finalizing models and methods to measure restoration success across these communities and compare restoration alternatives
Finalizing an overall index of amphibian community integrity
Person who carried out this activity:
954 577-6305 (voice)
954 577-6347 (FAX)
ken_g_rice@usgs.gov
Donnelly, M. A. Guyer, C.,; Juterbock, J. E, 1994, Techniques for marking amphibians: Smithsonian Institution, Washington, DC.
W. R. Heyer, M. A. Donnelly, R. W. McDiarmid, L. C. Hayek, and M. S. Foster, editors
MacKenzie, D. I., Nichols, J. D.; Lachman, G, 2002, Estimating site occupancy rates when detection probabilities are less than one: Ecology V. 83, n. 8, Ecological Society of America, Washington, DC.
Williams, B. K. Nichols, J. D.; Conroy, M. , 2002, Analysis and management of animal populations: Academic Press, London, England, UK.
Maskell, Andrew J. Waddle, J. Hardin; Rice, Ke, 2003, Osteopilus septentrionalis (Cuban Treefrog) Diet: Herpetological Review V. 34, n. 2, Society for the Study of Amphibians and Reptiles, Laclede, MO.
Waddle, J. H. Rice, K. G.; Percival H. F., 2003, Using personal digital assistants for collection of wildlife field data: Bulletin of the Wildlife Society v. 31, n. 1, The Wildlife Society, Bethesda, MD.
Dalrymple, G. H., 1988, The herpetofauna of Long Pine Key, Everglades National Park, in relation to vegetation and hydrology: General Technical Report RM-166, U.S. Department of Agriculture, U.S. Forest Service Symposium, Flagstaff, AZ.
Szaro, R. C., Stevenson, K. E., and Patton, D. R., editors
Duellman, W. E. Schwartz, A., 1958, Amphibians and reptiles of southern Florida: Bulletin n. 3, Florida State Museum, Gainesville, Florida.
Meshaka, D. I. Loftus, W. F.; Steiner, T., 2000, The Herpetofauna of Everglades National Park: Florida Scientist v. 63, n. 2, Florida Academy of Sciences, Orlando, FL.
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- Any data are subject to change and are not citeable until reviewed and approved for official publication.
954 577-6305 (voice)
954 577-6347 (FAX)
ken_g_rice@usgs.gov
amphibian community data in BICY
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Contact Kenneth G. Rice for data from this project.
727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov
U.S. Department of the Interior, U.S. Geological Survey
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